Im-trityl protection of histidine.

A rational attempt to prepare FmocHis(piTrt)OH regiospecifically gave in fact the well-known tau-trityl isomer, and experiments with model systems indicate that the prospects for access to pi-trityl histidine derivatives, which would be of great value for the racemization-free synthesis of histidine-containing peptides, are poor.     

The destruction of spores of Bacillus subtilis by the combined effects of hydrogen peroxide and ultraviolet light

Ultraviolet light irradiation of bacterial spores in the presence of hydrogen peroxide has been shown to produce synergistic kills when compared with ultraviolet light (u.v.) and hydrogen peroxide used sequentially. This use in combination has been patented for the commercial sterilization of packaging before filling with UHT-processed products. Previous results have shown that lamps producing u.v. light with a maximum output at about 254 nm were extremely effective. Results obtained using a Synchrotron radiation source to produce a narrow band of irradiation now shows that the greatest kill of spores of Bacillus subtilis in the presence of hydrogen peroxide is obtained with radiation at ˜270 nm. Such results suggest that the action of the u.v. light is not directly on the spore DNA but may be related to the production of free hydroxyl radicals from hydrogen peroxide.     

Modulation of antigen presentation and peptide-MHC-specific, LFA-1-dependent T cell-macrophage adhesion

Incubation of peritoneal macrophages in vitro before fixation increased their ability to present exogenous peptides to 3A9 T hybridoma cells. The enhanced level of presentation correlated with a greatly increased, peptide-specific adhesion of 3A9 cells to the macrophages, whereas peptide-independent adhesion was minimal and essentially unaltered. 3A9 cells exhibited rapid peptide-specific adhesion (plateau by 5 to 10 min) and deadhesion (complete reversal by 5 min). Peptide-specific adhesion was blocked by anti-I-Ak and anti-LFA-1. Interaction of T cell receptors and CD-4 with peptide-I-Ak complexes appeared to provide little direct contribution to the avidity of T cell-macrophage adhesion, but activated a LFA-1-mediated adhesion mechanism. In addition, anti-T cell receptor, anti-CD3, and anti-CD4 antibodies themselves activated LFA-1-dependent adhesion in the absence of peptide. Unlike the peptide-induced adhesion, this adhesion was similar for macrophages whether or not they were incubated in vitro before fixation. We conclude that the different macrophage populations supported LFA-1-mediated adhesion equally. Therefore, the enhancement of T cell stimulation observed after in vitro incubation of macrophages was due to increased peptide presentation and consequently increased triggering of LFA-1-mediated adhesion. Mechanisms may exist to regulate the effectiveness with which peptide-class II MHC complexes are displayed for T cell recognition.     

Angiotensin III and IV activation of the brain AT1 receptor subtype in cardiovascular function

The present investigation determined that native angiotensins II and III (ANG II and III) were equipotent as pressor agents when ICV infused in alert rats, whereas native angiotensin IV (ANG IV) was less potent. An analogue of each of these angiotensins was prepared with a hydroxyethylamine (HEA) amide bond replacement at the N-terminus, yielding additional resistance to degradation. These three angiotensin analogues, HEA-ANG II, HEA-ANG III, and HEA-ANG IV, were equivalent with respect to maximum elevation in pressor responses when ICV infused; and each evidenced significantly extended durations of effect compared with their respective native angiotensin. Comparing analogues, HEA-ANG II had a significantly longer effect compared with HEA-ANG III, and HEA-ANG IV, whereas the latter were equivalent. Pretreatment with the AT₁ receptor subtype antagonist, Losartan (DuP753), blocked subsequent pressor responses to each of these analogues, suggesting that these responses were mediated by the AT₁ receptor subtype. Pretreatment with the specific AT₄ receptor subtype antagonist, Divalinal (HED 1291), failed to influence pressor responses induced by the subsequent infusion of these analogues. These results suggest an important role for Ang III, and perhaps ANG IV, in brain angiotensin pressor responses mediated by the AT₁ receptor subtype.     

Effect of surfactant-associated protein-A (SP-A) on the activity of lipid extract surfactant

The properties of natural bovine surfactant and its lipid extract have been examined with a pulsating bubble surfactometer which assesses the ability of surfactant lipids to adsorb to the air/liquid interface and reduce the surface tension to near 0 dynes/cm during dynamic compression. Studies conducted at 1 mg/ml phospholipid revealed that the surface activity (i.e., the ability to produce low surface tensions) of lipid extracts could be enhanced by incubating the sample at 37 degrees C for 120 min or by addition of CaCl2. In contrast, incubation at 37 degrees C only slightly improved the biophysical activity of natural surfactant and the addition of CaCl2 had a more modest effect than with lipid extracts. With 20 mM CaCl2, the surfactant activity of lipid extract surfactant was similar to that of natural surfactant. Incubation with EDTA reduced the biophysical activity of natural surfactant. Experiments in which increasing amounts of lipid extract were replaced by natural surfactant revealed that small amounts of natural surfactant enhanced the surfactant activity of lipid extract. The biophysical activity of lipid extract surfactant was also increased by the addition of soluble surfactant-associated protein-A (SP-A) (28-36 kDa) purified from natural bovine surfactant. These results indicate that SP-A (28-36 kDa) improves the surfactant activity of lipid extracts by enhancing the rate of adsorption and/or spreading of phospholipid at the air/liquid interface resulting in the formation of a stable lipid monolayer at lower bulk concentrations of either phospholipid or calcium.     

Characterization of CDPdiacylglycerol hydrolase in mitochondrial and microsomal fractions from rat lung

CDPdiacylglycerol pyrophosphatase (E.C. 3.6.1.26) activity has been examined in rat lung mitochondrial and microsomal fractions. While the mitochondrial hydrolase exhibited a broad pH optimum from pH 6-8, the microsomal activity decreased rapidly above pH 6.5. Apparent Km values of 36.2 and 23.6 microM and Vmax values of 311 and 197 pmol.min-1.mg protein-1 were observed for the mitochondrial and microsomal preparations, respectively. Addition of parachloromercuriphenylsulphonic acid led to a marked inhibition of the microsomal fraction but slightly stimulated the mitochondrial activity at low concentrations. Mercuric ions were inhibitory with both fractions. Although biosynthetic reactions utilizing CDPdiacylglycerol require divalent cations, addition of Mg2+, Mn2+, Ca2+, Zn2+, Co2+, and Cu2+ all inhibited the catabolic CDPdiacylglycerol hydrolase activity in both fractions. EDTA and EGTA also produced an inhibitory effect, especially with the mitochondrial fraction. Although addition of either adenine or cytidine nucleotides led to a decrease in activity with both fractions, the marked susceptibility to AMP previously reported for this enzyme in Escherichia coli membranes, guinea pig brain lysosomes, and pig liver mitochondria was not observed. These results indicate that rat lung mitochondria and microsomes contain specific CDPdiacylglycerol hydrolase activities, which could influence the rate of formation of phosphatidylinositol and phosphatidylglycerol for pulmonary surfactant.